Add loading of a single level of includes from configuration files

[ntninja]

So far I was not able to compile it locally.

Fixes #1492

[ntninja]

Well, suggesting go install github.com/goreleaser/goreleaser@latest is a bad idea given it requires over 4GiB to compile and takes who-knows-how-long to build.

[ntninja]

Locally built and tested now.

Go remains an appalling minefield of inconsistencies as always, though…

[binwiederhier]

It's not Go. It's the CLI library. It's neat but that yaml stuff is wild and confusing

[ntninja]

Well, I didn’t interact with the CLI library at all for this, so I’ll take your word on the joy that may have been. For this code it was things like “oh look, structs are passed by value, slices are semantically passed by value but internally passed by reference, but maps are semantically and internally passed by reference” (I fail to see the logic behind this). Or the whole x := expr vs x, ok := expr thing… Or Go’s focus on concurrency, while making race-conditions the default (unless you can use a channel, another tuckered-on odd-ball feature). I just wished Go had been developed with the consistency of D, rather than the exceptionality-ness of JavaScript. It’d be a great language then, oh well…

What’s your take on the code?